The present invention relates to a process for treating substances in liquid, semi-liquid or paste form by another, notably gaseous phase.
It especially applies to the treatment of materials in liquid form with or without solid materials in suspension therein, by means of a gas at high temperature.
This is a typical problem, for example, in the case of treating waste water capable of yielding oxidation dried materials.
Many solutions have already been proposed to solve this problem.
For example, in French patent No. 2,075,354, it was proposed to eliminate liquid industrial wastes by conversion to solid wastes by treatment with a silicate solution and a solidification agent of said silicate.
It has been found that this is not a simple solution to the problem because it calls for the addition of compounds to the waste water, involves several steps and leads to a compound which itself should even be eliminated, and which, in the above-indicated case, compels solid residues resistant to water dilution to be obtained so that they may be incorporated into certain soils for enrichment.
A totally different solution is disclosed in French patent No. 2,320,268. This consists of contacting water, at a pH below 7 and at a temperture between 20.degree. and 200.degree. C., with pure technical oxygen, at pressure between normal pressure and 20 bars, until the sulfur is converted to thiosulfates. Then transforming the thiosulfates into sulfates by the action of technical oxygen at a pH from 0 to 5, or from 0 to 8 for waste water containing only sulfates, at temperatures of between 20.degree. to 200.degree. C., at pressure up to 20 bars, and possibly in the presence of catalysts.
It can be seen that this solution is equally time consuming and also calls for several operations involving physical and chemical processes.
More recently, in French application No. 773,154 filed Oct. 20, 1977, it was proposed to subject these waste waters simultaneously to pulverization and an oxidizing heat treatment and then to separate the solid residues from the volatile compounds in a simple manner.
It was proposed to implement the process in French patent No. 2,257,326, corresponding to our co-pending application Ser. No. 916,477, filed June 19, 1978, as a continuation of application Ser. No. 770,802, filed Apr. 19, 1977 (now abandoned), which was filed as a continuation of application Ser. No. 479,774, filed June 17, 1974, now abandoned, which co-pending application is incorporated herein by reference, and according to which substances in different phases are put into contact with each other. According to the present invention, at least one phase is used to form an axially symmetrical helical flow and at least one phase is introduced according to the symmetry axis of said helical flow until, in the reduced pressure zone of said helical flow, the momentum of the volume elements of the axial phase is such that said helical flow simultaneously causes the disintegration, dispersion and taking over of the axial phase and its eventual treatment by the helical flow.
However, the treatment conditions are very exacting, requiring temperatures of approximately 900.degree. to 1200.degree. C.
This involves contact heads which are able to withstand similar temperatures and resist the action of products treated at these temperatures as well as in an oxidizing medium, which is not the case for typical atomization heads.
It is for this reason that, in French application No. 78,07248 filed Mar. 14, 1978, in the name of the applicants, a new device was proposed to implement the process in French patent No. 2,257,326. The device comprises an assembly to form the helical flow composed of an element of rotation defining an annulus, in which the gaseous phase is tangentially introduced, limited by a divider element with axial symmetry conferring axial symmetry on the thusly formed helicoidal flow. The above-mentioned divider is mechanically independent of the rigid assembly for rotation.
In this way, the assembly can be cooled satisfactorily and the gaseous phase can be brought to a very high temperature.
Unfortunately, production of such a device is not always easy and we have found that excellent results could be obtained more simply with the process of this invention.